Power converter having airplane power source detector

ABSTRACT

A power converter having an aircraft power source detector adapted to limit the amount of power that can be drawn by the power converter when utilized in an aircraft. The power converter may detect an artifact of the aircraft power source, such as the 400 Hz ripple noise on an aircraft power line, or existing in the aircraft cabin, such EMI or aircraft lighting.

FIELD OF THE INVENTION

The present invention is generally related to power converters adaptedto power portable electronic devices, and more particularly to powerconverters adapted to be utilized in aircraft and subject to powerlimitations.

BACKGROUND OF THE INVENTION

Power converters, including those adapted to operate from DC powersources provided by vehicles and other DC power sources, may includewhat is commonly referred to as a cigarette lighter adapter (CLA). ThisCLA typically includes a DC/DC or AC/DC power converter adapted toconvert an input voltage of the power source to an output DC voltagesuitable for powering a portable electronic device. This CLA may beadapted to limit the voltage output and/or current output therefrom dueto the needs of a device to be powered, and due to other safety andcertification agency requirements.

Some CLA power adapters are also adapted to be used in aircraft socketsprovided proximate the passenger seats, allowing the passenger to powernotebook computers, MP3 players and other portable electronic devices.Aircraft power sources typically provide a higher DC voltage such as16-24 VDC, than provided by automobiles, such as 12-14 VDC. Due tosafety concerns, and load balancing, there are requirements that CLApower adapters not be permitted to draw more than a predetermined powerlimit, such as 60 watts. Power systems deployed within the aircrafttypically limit the amount of power that can be delivered to any onepower socket accessible by the passenger. Some aircraft include safetymechanisms that will crowbar, or become deactivated, if a CLA attemptsto draw more than 60 watts.

There is desired an improved power converter, such as a CLA powerconverter/adapter, that automatically limits power drawn from anaircraft power source to no more than a predetermined limit, such as 60watts.

SUMMARY OF INVENTION

The present invention achieves technical advantages as a power converterhaving an aircraft power source detector adapted to limit the amount ofpower that can be drawn by the power converter when utilized in anaircraft.

In a first embodiment of the present invention, the power converter isadapted to physically sense the presence of an aircraft socket adaptedto deliver power thereto. The power converter may be powered with amechanism to detect an annular bar within the socket of the aircraftpower source, which bar is conventionally provided in an aircraft socketand utilized to allow the aircraft to detect the presence of anelectronic device. Power may only be provided to this socket when thisbar is depressed by a converter disposed within the socket, such as aCLA. The present invention is provided with a mechanism to detect thepresence of this bar, and automatically limits the power converter fromdrawing power no greater than a predetermined limit specified for theaircraft, such as 60 watts. In a second embodiment of the presentinvention, the power converter is provided with electronics detectingthe presence of an aircraft power source. Aircraft providing power topassengers typically draw power generated by an auxiliary power unit(APU) of the aircraft, the aircraft engines or ground power units. Theuse of the acronym APU from here on will include the several sources ofaircraft AC power mentioned above. Conventionally, this APU providespower to the aircraft, and also to the passenger's seats. The APU ischaracterized in that a 400 Hz frequency component is typicallygenerated by the APU, which is detectable as a 400 Hz noise ripple onthe power line. This 400 Hz frequency component is also detectablewithin the ambient of the aircraft cabin as an electromagneticinterference (EMI) signal, or detectable in the aircraft lighting. Thepresent invention is adapted to detect this 400 Hz frequency componentor its artifacts, either existing on the power line or within thepassenger cabin, to determine that the power source coupled to theconverter is that generated by an aircraft. Upon detection of this 400Hz frequency component or its artifacts, the power converter is adaptedto limit its power draw from the aircraft power source. Detection of thepower line voltage may also be analyzed to determine if the power may beaircraft power, such as the voltage exceeding a threshold, such as 14.5volts DC.

In a third embodiment of the present invention, an adaptation of the CLAis useable in aircraft. The connector consists of two power pins and twosense pins. A potential can be measured between pins A and B, such as 3V. Power may only be provided to a power adapter when an impedance, suchas 300 ohms, is placed between pin A and pin B as shown in the FIG. 4and 7. If the impedance is divided into two parts by resistor R1 and R2then the presence of a voltage at diode D3 indicates the presence of anaircraft by opamp U1.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view of a power converter according to a first embodiment ofthe present invention;

FIG. 2 is a cross sectional view taken along line 2-2 in FIG. 1;

FIG. 3 is an electrical block diagram of the power converter shown inFIG. 1 including a control circuit;

FIG. 4 is an electrical schematic of one embodiment of the presentinvention adapted to detect that the input power is provided by anaircraft;

FIG. 5 is a second embodiment of the present invention adapted to detecta frequency component on the input power line generated by the aircraft,and/or as an EMI signal within the passenger cabin;

FIG. 6 is a block diagram showing an implementation with temporaryloading to allow reliable detection of the 400 Hz artifacts from theinput power line; and

FIG. 7 is a diagram showing the mechanical connection of the invention.

DETAILED DESCRIPTION OF THE PRESENT INVENTION

FIG. 1 depicts a side view of a power converter 10 according to a firstembodiment of the present invention. Power converter 10 is seen tocomprise of a power converter configured as cigarette lighter adapter(CLA) power converter, although limitation to this specific mechanicaldesign is not to be inferred. The converter may comprise of a DC/DC oran AC/DC converter as desired. CLA 10 is seen to include an elongatedcylindrical body 12 having an electrode 14 on a proximal end thereofadapted to make physical and electrical contact with the positiveterminal within a power socket deployed in an aircraft, as well as thatavailable in an automobile or other vehicle. A second electrode 16,configured as a series of annular spring-leaf members, forms thenegative terminal for the power converter 10, and is seen to beelectrically separated from terminal 14 by a dielectric portion 18disposed therebetween. Notably, the negative electrode 16 is moved moreforward toward the proximal end of the CLA converter 10 than thattypically utilized in standard automobile CLA adapters. Advantageously,this negative electrode 16 is disposed closely proximate the distal endof the body 12, and proximate the electrode 14, so as to be physicallyand electrically separated from a midsection thereof.

Still referring to FIG. 1, there is shown disposed about the midsectionof the body 12 an annular member 20, that may resemble an annularbumper. This annular member can be inwardly biased toward the body 12when physically interfaced with the bar (not shown) typically deployedwithin a power socket deployed within an aircraft, such as under theseat, or adjacent an armrest. This displaced annular member isdetectable by a control circuit 40, shown in FIG. 4, and which will bedescribed in more detail shortly. Upon 7 detection of this annularmember displacement, the power converter is adapted to draw no more thana maximum predetermined power from the aircraft socket, via electrodes14 and 16, such as 60 watts. Power converter 10 is further seen toinclude a power cord 22 extending from the power converter 10 andadapted to connect to a portable electronic device for powering thereof,such as via a connector. Power cord 22 extends from an interface 24,which my comprise of a connector providing a DC voltage on one conductorand ground on the other. Alternatively, power cord 22 can be hard wiredto the power converter circuitry within power converter 10.

Referring now to FIG. 2, there is shown a cross sectional view takenalong line 2-2 in FIG. 1, illustrating the cylindrical body 12 and theannular displaceable member 20. The ground electrode 16 is seen to beelectrically connected to the power converter circuit 30 disposed withinthe housing 12.

Referring now to FIG. 3, there is shown an electrical block diagram ofthe power converter 10 seen to include the power converter circuitry 30,and in addition, a control 32. Control 32 may be comprised of amechanical mechanism for detecting the presence of aircraft socket, or,as an electrical circuit configured to sense an electrical parameterprovided on either of power lines 36 and 38 extending from electrodes 14and 18.

In the embodiment shown in FIG. 1, control 32 is illustrated in blockdiagram form as a displaceable mechanical mechanism adapted to providean indication on line 34 to power converter circuitry 30 that theconverter 10 is inserted into the socket of an aircraft. Power convertercircuitry 30 is functionality responsive to this indication andresponsively limits the amount of power delivered to output terminal 34to a predetermined limit, such as 60 watts. Should a user utilize thepower converter 10 to power a portable electronic device, the powerdrawn is limited to this predetermined limit. This provides an automaticsafety mechanism to avoid overloading the aircraft socket, the aircraftpower system, and to avoid heat or other safety hazards.

In another embodiment of the invention, the control device 32 iscomprised of an electrical circuit electrically coupled to lines 36 and38 adapted to detect an electrical parameter of the aircraft powersystem, such as a 400 Hz carrier generated by the APU of the aircraft,or other electrical component generated by the APU. Conventionally, theonboard APU of the aircraft provides a small amount of noise on thepower system, detectable as an AC ripple carried on the DC power lineprovided to electrode 14. This 400 Hz frequency component or itsartifacts may also be detectable on the ground of the electrical system,depending on the electrical configuration. The aircraft power system isdesigned to minimize this 400 Hz carrier or artifacts; however, itexists even at a very minimal level and is detectable by a control 32.Control 32, upon detection of this 400 Hz carrier or artifacts, providesan electrical signal on line 34 to the power converter circuit 30,indicating the presence of an aircraft power system. Again, powerconverter circuit 30 limits the output power provided to terminal 24upon detection thereof, and may modify the processing of power drawntherefrom if desired. In one embodiment, the 400 Hz carrier may berectified by a full-wave rectifier, and a detector may detect theresulting 800 Hz waveform.

In yet another embodiment, control 32 may detect the presence of the 400Hz frequency component as EMI interference within the passenger cabin,detectable via a small RF antenna. Upon detection of this 400 Hzfrequency component, the control 32 also provides the signal on line 34indicative of this 400 Hz carrier. Control 32 may also detect thepresence of the 400 Hz frequency component affecting the aircraft cabinlighting, such as using a photocell, photodiode or other devise.

Referring now to FIG. 4, there is shown at 40 one embodiment of acircuit adapted to respond to mechanical embodiment of the invention,such as that shown in FIG. 1. Switch SW1 is electrically represented asthe deflectable annular member 20 in FIG. 1, and normally provides powerfrom electrode 14 to the power converter circuit 30 when not displaced.When the annular member 20 is compressed, such as due to engagement withthe bar in the aircraft socket, switch SW1 closes and communicates thepositive voltage from electrode 14 thru a series of components to an opamp U1, which compares a conditioned voltage to a reference voltage.When switch SW1 is closed, op amp U1 is configured to generate a signalat output 34 which indicates that switch SW1 is closed, indicating thepresence of an aircraft power source. FIG. 4 and 7 also show points Aand B, which when connected together with predetermined impedance,allows the aircraft to supply power to a power product. The potentialthat is applied between points A and B is conditioned and compared atthe operational amp U1 to a reference voltage. The operational amplifierthen produces a signal at 34 to indicate that an aircraft has beendetected.

Referring to FIG. 5, there is shown an electrical block diagram of acircuit 50 adapted to detect the 400 Hz carrier or artifact on theaircraft power system as provided via electrode 14. In one embodiment, adetector circuit 52 may comprise of a tuned amplifier having a filteradapted to detect the aircraft 400 Hz carrier, and which filter has abandwidth sufficiently narrow to reject other frequencies that may bepresent on the power line, such as 60 Hz. In another embodiment, thedetector circuit 52 may comprise of a phase locked loop (PLL) or otherelectrical circuits that can detect the presence of the 400 Hz carrieror artifact seen as a noise on the aircraft power line, such as aharmonic of the carrier. Circuit 52 generates an electrical signal online 34 as previously described utilized by converter circuitry 30 todiscern the presence of an aircraft power source. The detector circuit52 may also comprise of a low frequency analog filter, such as agyrator, a turned digital filter, or a resonant tank.

Also shown in FIG. 5 is a circuit 54 comprising a capacitor platemounted inside the converter 10 and adapted to detect the airbornepresence of the 400 Hz signal. The 400 Hz airborne frequency componentis essentially an RF EMI signal that can be received via the capacitorplate 54, or other suitable antenna mechanism.

The detection of this 400 Hz aircraft frequency component may also beused by power converter circuitry 30 to modify its signal processing andoperation when it knows it is operating from an aircraft power system.For instance, additional filtering or gain adjustments may beautomatically or selectively made upon indication of the aircraft powersystem.

The AC line frequency typically existing in commercial airliners andground support systems is typically in the range of 400 Hz +/−12%.Accordingly, the signal processing capability of control circuit 30would be available to detect a carrier frequency within this tolerance.

Still referring to FIG. 5, capacitor C1 is a coupling capacitor thatconnects either directly to the power input line of the aircraft system,or to the capacitor metal plate mounted within the power converterhousing. For direct connections, the input could be DC or AC sinceeither type of voltage can be available, depending on the aircraft. Forindirect connection, the metal plate is capacity coupled, as discussed,to couple any 400 Hz electrical field present in the aircraft cabin.

The advantage of a PLL circuit as the control 32 is that the PLL circuitcan operate within a narrow band and track the frequency componentsignal if its frequency varies.

The circuit of FIG. 6 shows the implementation of the previouslymentioned filters and phase locked loop decoder. Additionally, atemporary loading circuit has been added that is controlled by a timer.This timer operates briefly when power is first applied. During theinterval when the timer operates, a loading resistor is switched ontothe input power line and this causes the ripple from the input powersource to increase. During this time of increased ripple the ability ofthe circuit within the dotted lines to detect the 400 Hz signal or itsartifacts is enhanced. This leads to quicker and more accuratedetection.

Though the invention has been described with respect to a specificpreferred embodiment, many variations and modifications will becomeapparent to those skilled in the art upon reading the presentapplication. It is therefore the intention that the appended claims beinterpreted as broadly as possible in view of the prior art to includeall such variations and modifications.

1. A power converter, comprising: a first circuit having an inputadapted to receive a power source having a first voltage, and adapted toconvert the first voltage to a second voltage provided to an output, thefirst circuit adapted to power a portable electronic device; and asecond circuit coupled to the first circuit and adapted to identify ifthe power source as an aircraft power source.
 2. The power converter asspecified in claim 1 wherein the first circuit is adapted to respond tothe first circuit when the aircraft power source is detected.
 3. Thepower converter as specified in claim 2 wherein the first circuit limitsan output power provided to output when the aircraft power source isdetected.
 4. The power converter as specified in claim 3 wherein thefirst circuit limits a current of the output power when the aircraftpower source is detected.
 5. The power converter as specified in claim 1wherein the second circuit detects a frequency component of the powersource.
 6. The power converter as specified in claim 1 wherein thesecond circuit detects the absence of a frequency component of the powersource.
 7. The power converter as specified in claim 5 wherein thesecond circuit detects a presence of generally a 400 Hz signal providedby the power source.
 8. The power converter as specified in claim 6wherein the second circuit detects the absence of generally a 50-60 Hzsignal provided by the power source.
 9. The power converter as specifiedin claim 1 wherein the power converter further includes a connectoradapted to couple to the aircraft power source.
 10. The power converteras specified in claim 9 wherein the converter has a displaceable memberadapted to determine if the power source is provided by the aircraftpower source.
 11. The power converter as specified in claim 10 whereinthe member is adapted to be displaced upon coupling to the aircraftpower source.
 12. The power converter as specified in claim 11 whereinthe connector comprises a plug including the member.
 13. The powerconverter as specified in claim 12 wherein the member is adapted to bedepressed upon coupling of the connector to the aircraft power source.14. The power converter as specified in claim 13 wherein the member isadapted to be depressed by a member forming a portion of the aircraftpower source.
 15. The power converter as specified in claim 14 whereinthe portion comprises a protruding said member.
 16. The power converteras specified in claim 15 wherein the protruding member comprises anannular member.
 17. The power converter as specified in claim 9 whereinthe connector comprises a plug.
 18. The power converter as specified inclaim 5 wherein second circuit is adapted to be electrically coupled tothe aircraft power source.
 19. The power converter as specified in claim18 wherein the converter further includes a connector adapted to coupleto the aircraft power source.
 20. The power converter as specified inclaim 19 wherein the connector couples the aircraft power source to thesecond circuit.
 21. The power converter as specified in claim 20 whereinthe connector comprises a plug.
 22. The power converter as specified inclaim 21 wherein the plug has an electrode adapted to couple to theaircraft power source.
 23. The power converter as specified in claim 22wherein the plug is adapted to couple to a receptacle of the aircraftpower source.
 24. The power converter as specified in claim 5 whereinthe second circuit comprises a receiver adapted to wirelessly sense thefrequency component of the power source.
 25. The power converter asspecified in claim 5 wherein the second circuit comprises a filtercircuit adapted to filter the frequency component from the power source.26. The power converter as specified in claim 26 wherein the filter isselected from the group consisting of a gyrator, a tuned digital filter,a phase locked loop, and a resonant tank.
 27. The power converter asspecified in claim 5 wherein the second circuit is adapted to detect thefrequency component of an aircraft auxiliary power unit (APU).
 28. Thepower converter as specified in claim 1 wherein the second circuitcomprises a switch adapted to switch states upon the second circuitcoupling to the aircraft power source.
 29. The power converter asspecified in claim 1 wherein the second circuit provides a signal at theoutput indicative of the presence of the aircraft power source.
 30. Thepower converter as specified in claim 1 wherein the second circuitdetects an artifact of the aircraft power source.
 31. The powerconverter as specified in claim 5 further comprising a loading circuitconfigured to be selectively coupled to the second circuit and enhancesignal detection of the frequency component.